I think you have given a clue as to the problem Riley
I presume you had the tank off for the plug change etc. ?
Often a trapped fuel/breather pipe can present these symptoms
Particularly with "vacuum" type fuel taps
Is yours a diaphram tap ?
(Yams usually are
)
Could be a classic case of fuel starvation m8
Don't abandon all hope yet
It's quite likely to be something minor